European prospects for phosphate recovery from sewage

Issue:

The future looks brighter for the recycling of phosphates following the recent publication by the European Commission of proposed changes to regulations on fertiliser certification, but use of sewage sludge remains controversial and has been excluded from those changes. Keith Hayward spoke with Chris Thornton of the European Phosphates Platform about the proposals and the prospects for products based on struvite sourced from sewage sludge.

Spreading fertiliser, (c) Shutterstock / oticki

We are entering a new phase in the way the world views and deals with phosphates, believes Chris Thornton of the European Sustainable Phosphorus Platform. We have been variously through a period of raised concern with little action, a period of escalated phosphate rock and food prices rises in the wake of the Arab Spring, and more recently a period of alarm, thanks in particular to the attention drawn to the issue by Dana Cordell in her seminal thesis of 2010, that we may be running out of this vital sustainer of agricultural production. The new phase that is emerging is one in which at last there is the prospect of taking a new approach, at least in Europe: the circular economy.

‘The problem is not that phosphate is running out, but that it is not running out and we keep putting it into the environment,’ says Thornton. He points out that phosphate pollution is the second largest cause of surface waters not achieving their target ecological status in Europe, second only to their physical modification.

Having said this, there are concerns around Europe’s ability to source phosphates in future, even if globally we may not run out as quickly as some have predicted. ‘It is clearly true that resources are concentrated,’ says Thornton. The main reserves include those held by China, Saudia Arabia, Iraq and Morocco, the latter being the continent’s main current supplier.

Chris Thornton

Thornton points also to other reasons why politicians and policy makers are interested in moving towards a circular economy approach. For example, the end use of recycled materials in agriculture represents an opportunity to help revive rural areas. ‘The circular economy is where things are going, and the recycling of nutrients and organic carbon is particularly interesting because it will generate decentralised rural jobs,’ says Thornton.

Prospects for sewage sludge

All of this sounds promising for the future recycling of phosphates, and the European Commission has indeed launched its first circular economy initiatives over recent months. A big question as far as those in the water industry are concerned is what this shift will mean for sewage sludge, since this can provide a rich source of phosphates. Many countries recycle sewage sludge to agriculture, but there are potential benefits in producing refined fertiliser products.

One of the European Commission’s biggest steps to date has been to publish proposals for revision of the EU Fertiliser Regulations. The regulations allow Europe-wide certification of fertiliser products, with the aim of making market access easier by overcoming the need for products to obtain approval for sale on a country-by-country basis.

The existing regulations are limited to the recycling of inorganic sources, but the proposed revisions would extend the regulations to organic sources. However, the proposals specifically exclude sewage sludge as a source material at this time. ‘Recycling sewage sludge to land is controversial,’ notes Thornton. This is because of concerns over what contaminants are in the sludge, including pharmaceuticals.

There is a range of options for creating recycled products, and individual countries remain free to approve products on a national basis. Such concerns have however made it difficult for the Commission to bring forward regulations on sludge in the past, so the current exclusion is a tactical move to help ensure the new regulations can obtain approval, Thornton says.

As discussed in the following articles, phosphate recovered in the form of struvite presents one of the clearest opportunities for recycling. The European Commission has asked its Joint Research Centre to develop a specification for struvite products in anticipation of allowing them under the new fertiliser regulations once these are approved. ‘Struvite will be the first example, hopefully, of a sewage-based product being authorised in the EU Fertiliser Regulation,’ comments Thornton.

Thornton observes that even for struvite there could be concerns over the presence of trace micropollutants. Such concerns, for struvite and regarding sludge generally, should not be dismissed, but at the same time there are wider reasons for progressing with resource recovery. ‘Those [concerns] need to be taken very seriously,’ says Thornton. ‘The important thing is to ensure that we manage those concerns but that we do allow development of recycling of sewage sludge products to land.’